For the purpose of reducing the weight of metal parts while giving them greater strength, especially in tension or in compression, it is known to incorporate ceramic fibers thereinto. For example, these are silicon carbide (SiC) fibers which have a tensile strength and a compressive strength that are substantially greater than that of a metal such as titanium.
The manufacture of these parts involves the prior formation of inserts from ceramic filaments with a metal matrix, which inserts comprise a ceramic fiber coated with metal. They are also referred to as CMM fibers or coated filaments. The metal gives the elasticity and flexibility necessary for handling them.
A known process for manufacturing such reinforced parts comprises the production of a winding of a coated filament around a mandrel. The winding is then introduced into a main metal body or container in which a slot forming the housing for the insert has been machined beforehand. The depth of the slot is greater than the height of the winding. A cover is placed on the container and welded to its periphery. The cover has a tenon having a shape complementary to that of the slot, and its height is adapted to that of the winding placed in the slot so as to fill the slot. Next, a hot isostatic pressing step is carried out, during which the cover is deformed and the winding is compressed by the tenon.
The hot isostatic pressing technique consists in placing the part in an enclosure subjected to high pressure, of the order of 1000 bar, and also to high temperature, of the order of 1000° C., for a few hours.
During this treatment, the metal sheaths of the coated filaments are welded together and to the walls of the slot by diffusion, to form a dense assembly composed of a metal alloy within which the ceramic fibers annularly extend. The part obtained is then machined to the desired shape.
The process serves for the manufacture of axisymmetric aeronautical parts, such as rotor disks or blisks (integrally bladed disks), but also shafts, actuator bodies, casings, etc.
It is difficult to machine the slot in the main body, especially because of the small radii in the bottom of the slot. This small radius is necessary in order to house the insert, which has a rectangular cross section. The machining of the corresponding tenon in the cover is not easy either, because of the non-open-ended corners.